Up front the only thing that got me frustrated was that once I added a shield or a barrel I couldn't undo it. Also I got a little confused at the beginning of the game, but a quick read from the game page got me ready for an amazing game.
Now for the praise. In my opinion the quality of a puzzle game is measured by how much I feel like a mad genius once I get to the solution. Not every puzzle game achieves this. This game (despite being done in only a week for a game jam) accomplished it incredibly.
Hope you don't feel I'm being exaggerated, but I genuinely found it very challenging, unique and fun. Incredible game design on your part, you really bent my brain all the way to the last level.
Fantastic work. Hope to play another one of your games in the future :)